Aluminum and aluminum alloys are both relatively soft and ductile metal materials, and deformation is a common problem in the preparation process of their metallographic samples. After preparation, a layer of oxide film will be formed on the surface, making corrosion difficult. The solution to these problems depends on the selection of metallographic sandpaper, polishing fluid, polishing cloth, and the specific preparation plan during the entire sample preparation process.

    Due to the widespread application of energy spectrum analysis in phase identification of aluminum and aluminum alloys, commercial grade aluminum and aluminum alloys generate different intermetallic compound particles with different compositions. Usually, these intermetallic compound particles are more susceptible to corrosion by corrosive agents than the substrate. Therefore, the metallographic sample preparation of aluminum and aluminum alloys can be carried out using a four step preparation method. (The following preparation method takes QMAXIS metallographic consumables as an example)

    Firstly, use 240 grit (P280) metallographic sandpaper to grind the surface of the sample, with a general grinding disc speed of 240-300 rpm and a load of 5Lb (22N), until the damaged layer on the sample surface caused by cutting is removed.


Grind with metallographic sandpaper of size 320 (P400) again, with the same speed and load as before, until all scratches from the previous grinding are removed.


The grinding step of metallographic sandpaper mainly involves removing the deformation layer on the surface of the sample, and smoothing the surface of the sample. This step is crucial. Whether the coarse grinding process of metallographic sandpaper is in place will directly affect the success or failure of the subsequent preparation process. Therefore, in the process of using metallographic sandpaper for grinding, it is necessary to choose the appropriate particle size label, pay attention to selecting high-quality metallographic sandpaper, and also pay attention to the specific operating process of grinding. The adjustment and determination of process plans require continuous accumulation of experience and summarization. Different experimental requirements and operations by different individuals may vary, so the plan provided by the editor is for your reference only.


After metallographic sandpaper grinding, the subsequent polishing process, selection of polishing fluid, polishing paste, polishing cloth, and specific polishing process are shown in the table below.

    The above four step sample preparation scheme can achieve ideal polishing results for many aluminum alloys. This method retains all intermetallic compound particles in the aluminum alloy and controls the buoyancy to a relatively small range. For very pure aluminum alloys, vibration polishing can be added later to improve surface smoothness. It is very difficult to prepare a completely scratch free surface for such aluminum alloy samples. For everyone's reference only!